Conventionally, a fastener joint that fix parts, which are objects to be joined, with each other by bolts and nuts is known as a method for joining composite materials, such as GFRP (glass fiber reinforced plastics) or CFRP (carbon fiber reinforced plastics), which are used as a material of a part of an aircraft or the like, with each other or a method for joining a composite material with a metal.
However, when fastener joints are required at many places like in a case of a joint of parts of an aircraft with each other, for example, increase in assembly man-hours and increase in the weight of a product are caused.
Thus, a technique using an adhesive joint for joining parts of an aircraft or the like with each other has been devised in expectation of a weight reduction compared with a fastener joint. For example, a scarf joint that cuts parts, which are objects to be joined, obliquely to each other in order to widen joint surfaces has been devised as an adhesive joint (for example, refer to U.S. Pat. No. 5,281,454 A).
A composite material is formed by laminating thin sheets, which are called prepregs and each made of reinforced fibers impregnated in a resin, and subsequently heating and curing the laminated sheets. Therefore, strength of a composite material in a lamination direction is small compared with strength in a direction along surfaces of prepregs.
Thus, a technique to place a metal sheet, such as a titanium sheet, between sheets of prepregs as a reinforcement member in order to secure strength of a composite material in the lamination direction has been devised (for example, refer to Japanese Patent Application Publication JP 2014-024334 A).
An object of the present invention is to further improve strength of an adhesive joint of a composite material.